Problem: Ashley is 4 times as old as Ishaan and is also 21 years older than Ishaan. How old is Ashley?
Solution: We can use the given information to write down two equations that describe the ages of Ashley and Ishaan. Let Ashley's current age be $a$ and Ishaan's current age be $i$ $a = 4i$ $a = i + 21$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $a$ is to solve the second equation for $i$ and substitute that value into the first equation. Solving our second equation for $i$ , we get: $i = a - 21$ . Substituting this into our first equation, we get the equation: $a = 4$ $(a - 21)$ which combines the information about $a$ from both of our original equations. Simplifying the right side of this equation, we get: $a = 4a - 84$ Solving for $a$ , we get: $3 a = 84$ $a = 28$.